Technical Abstract:
Crop and soil management may influence development and control of early and late blight; however, their effects are not well documented. From 2006-2008, we evaluated the effects of cropping system and irrigation on incidence and severity of early and late blight of potato, and on microclimatic parameters that influence disease development. Early blight was determined by visual assessment of symptoms in Status Quo (SQ), Soil Conserving (SC), Soil Improving (SI), Disease Suppressive (DS), and continuous potato (PP) cropping systems under both irrigated and rainfed management. Microclimatic data were recorded with a data logger at canopy level and used to predict late blight potential. Early blight incidence, severity, and lesion numbers varied among cropping systems and years. Disease incidence ranged from 31-64% (2006), 12-43% (2007), and 8-43% (2008), and was significantly higher in continuous potato than in DS, SQ, SC, and SI systems. In the same years, the number of lesions per plant ranged from 14-26, 11-36, and 2-14, respectively. Microclimate was not significantly correlated with early blight, implying the variables measured had little effect on pathogen development. Late blight potential was not influenced by soil, crop, or water management system, as fungicides were uniformly applied across experimental treatments. This research demonstrates that cropping systems can affect disease development and control as evident by greater early blight levels in continuous potato compared to other systems.